Integrated Health Monitoring Research Articles

An Integrated Health Monitoring System for Fission Surface Power

Abstract Based on such criteria as safety and mission success, programmatic risk, affordability, and extensibility/flexibility, the National Aeronautics and Space Administration (NASA) has chosen fission surface power (FSP) as the primary energy source for building a sustained human presence on the Moon, exploring Mars, and extremely long-duration space missions. The current benchmark FSP system has a mission life of at least 8 years during which time there is no opportunity for repair, sensor calibrations, or periodic maintenance tasks that are normally performed on terrestrial-based nuclear power plants during scheduled outages. Current technology relies heavily on real-time human interaction, monitoring and control. However; due to the long communication times between the Earth and Moon, or Mars, real-time human control is not possible, resulting in a critical need to develop autonomous health monitoring technology for FSP systems.This paper describes the design and development of an autonomous health monitoring system that will (1) provide on-line calibration monitoring, (2) reduce uncertainties in sensor measurements, and (3) provide sensor validation and fault detection capabilities for the control systems of various FSP subsystems. The health monitoring system design integrates a number of signal processing algorithms and techniques such as cross-calibration, empirical modeling using neural networks, and physical modeling under a modular signal processing platform that will enable robust sensor and system monitoring without the need for human interaction. Prototypes of the health monitoring system have been tested and validated on data acquired from preliminary subsystem testing of NASA's FSP Technology Demonstration Unit (TDU) as well as simulated laboratory data. Results from this testing have demonstrated the utility and benefits that such autonomous health monitoring systems can provide to FSP subsystems and other potential applications within NASA such as launch vehicle systems, other nuclear power systems, and ground operations.

Design of copper/carbon-coated fiber Bragg grating acoustic sensor net for integrated health monitoring of nuclear power plant

A nuclear power plant (NPP) is a harsh environment that gives rise to age-related degradation of the plant structures, and eventually leads to radiation leakage that threatens humans. Integrated structural health monitoring (ISHM) technology is a strong candidate for the prevention of the NPP accidents during operation. Prior studies have shown that fiber Bragg gratings (FBGs) and metal-coated fibers have good radiation and high temperature resistance. In this study, a FBG acoustic sensor using a metallic adhesive for installation and a relatively economical copper/carbon (Cu/C)-coated fiber is developed for ISHM of high temperature NPP structures. A chemical method is proposed to remove the Cu/C coating. A 5 mm FBG was successfully inscribed in a Ge-doped silica core through a 7 mm-long silica section with the coating removed. The Cu/C-coated fiber with the same core/clad structure as the standard SMF allowed no-loss fusion splicing, and showed good adaptability to the economical standard fiber, adaptor, connector, and instruments. It showed also good thermal resistance (<345 °C) with no degradation in optical power during the optical transmission. The metallic adhesive used to install the FBG in a one-end-free configuration showed superior bonding reliability during temperature cycles ranging from 25 °C to 345 °C. The FBG reflectivity was stabilized at a 58% drop from the initial reflectivity, and the Cu/C-coated FBG sensor using the metallic adhesive could successfully detect the acousto-ultrasonic waves generated by pencil lead breaking and laser beam excitation.

杭基礎の間接/直接統合ヘルスモニタリングに関する振動台実験

A series of shaking table tests on indirect-direct integrated health monitoring of pile foundations have been carried out for the purpose of detecting global and local damage during their service life. Different damage conditions of pile foundations are simulated. A limited number of acceleration sensors are placed on the roof and base of superstructure, whereas a number of strain sensors are attached to all piles at different depths. In the indirect health monitoring, the changes in transfer functions related to soil-structure interaction due to damage are investigated to detect global damage of piles. In the direct health monitoring, on the other hand, the changes in strain distribution of each pile due to damage are investigated to detect local damage of piles. Based on the experimental results, the feasibility of the real world application of the proposed method is discussed.

Integrated health monitoring for reinforced concrete beams: An experimental study

Civil infrastructures begin to deteriorate once they are built and used. Detecting the damages in a structure to maintain its safety is a topic that has received considerable attention in the literature in recent years. In vibration-based methods, the first few modes are used to assess the locations and the amount of damage. However, a small number of the global modes are not sufficient to reliably detect minor damage in the structure. Also, a common limitation of these techniques is that they require a high-fidelity model of the structure to start with, which is usually not available. Recently, guided waves (GWs) have been found as an effective and efficient way to detect incipient damages due to its capacity of relatively long propagation range as well as its flexibility in selecting sensitive mode-frequency combinations. In this paper, an integrated structural health monitoring test scheme is developed to detect damages in reinforced concrete (RC) beams. Each beam is loaded at the middle span progressively to damage. During each loading step, acoustic emission (AE) method is used as a passive monitoring method to catch the AE signals caused by the crack opening and propagation. After each loading step, vibration tests and GW tests are conducted as a combined active monitoring measure. The modal parameters and wave propagation results are used to derive the damage information. Experimental results show that the integrated method is efficient to detect incipient damages in RC structures.

Health monitoring of flexural steel structures based on distributed fibre optic sensors

In our previous study, a distributed long-gauge fibre optic sensing system (with the ability to obtain effective average strain, or macro-strain, distributions) for practical adaptation in civil structural health monitoring was developed and verified. The present paper is devoted to proposing an integrated health monitoring scheme for elastic beam-like structures, where flexure dominates structural responses, based on static testing and measurements using the developed sensors. A series of experimental investigations on steel beams with different levels of damage are first carried out. The static strain measurements from distributed sensors are characterised and some concerns on the data processing and feature extraction are discussed. On the basis of the extracted features, structural health monitoring (SHM) investigations are deployed in three parts: damage identification with no requirement for a structural analytical model, parametric estimation based on finite element (FE) models, and evaluation of structural global behaviour. By comparing to traditional transducers such as linear variable displacement transducers (LVDTs) and foil ‘point’ strain gauges, the ability and ascendancy of the sensors developed here for SHM purposes are verified. A comprehensive health monitoring strategy for steel flexural structures based on the distributed strain sensors array is proposed finally.

Piezoelectric Fiber Composites as Sensor Elements for Structural Health Monitoring and Adaptive Material Systems

Piezoelectric Active Fiber Composites (AFC) and Macro Fiber Composites (MFC) have the potential to provide various sensor functions for nondestructive test methods. AFC have been integrated into fiber-reinforced laminates as a first step towards structures with sensing capability. These developments constitute initial stages for developing adaptive composite structures or structures with integrated health monitoring system. So far, the use of AFC and MFC has been explored in selected nondestructive tests for defect detection in model composite systems on laboratory scale with e.g., Acoustic Emission, Acousto-Ultrasonics, and Electromechanical Impedance testing. The present article will focus on limitations and current prospects for structural health monitoring with AFC or MFC and discuss selected concepts and approaches.

Editorial for Special Issue

A “structure” is here understood to include anything constructed by man—underground space, buildings, transmission towers, pipelines, distribution grids, economic systems, air frames, measuring, data acquisition and manipulation systems, etc. The design and control of these infrastructure elements can all fit within the purview of Civil Engineering. They all affect the public wellbeing; they all involve aspects of what traditionalists define as civil engineering. Some elements demand expansion of expectations and imagination, but provide the profession with new opportunities in growing application spaces, provide powerful tools, more interesting and cutting edge problems to solve. This growth could also attract the attention of many students who currently choose other fields of engineering, science, public policy, business, and economics, and minimize reliance on other disciplines. The civil engineering profession has much to offer society, and everyone would benefit by our addressing more of the world. An example of the empowerment of civil engineers through integration of new technologies is enlightening. Integrated health monitoring of structures, made possible by advances in sensor technology, is improving structural reliability, longevity, system performance, and safety against natural hazards and intentional attack. Current technology is moving beyond the embryonic stage and is becoming able to meet the challenges associated with structural health interpretation. Perhaps the most important enabling technology for structural health monitoring has been the introduction of comprehensive miniature sensing platforms that colocate transduction sensing or actuation , signal processing, computational power, and wireless communication all in one miniaturized package. Such wireless sensors are commonly called motes, or “smart” sensors. In turn, motes are combined into large, organic networks that allow dense, detailed sensing, thereby opening a new sensing paradigm in which the network is effectively the sensor. The paradigm of sensor networking allows engineers and scientists to move beyond the idea of a sensor as a single instrument that only measures one thing, to a comprehensive system consisting of many small nodes working cooperatively. Motes are now ubiquitous enough that several companies, large and small, are selling them commercially. Today, civil engineers are in a good position to refine existing measurement archetypes by utilizing emerging sensor design archetypes; in particular, transducers and micro-circuitry made possible by micro electro-mechanical systems MEMS technology. MEMS are micron-scale mechanical devices that are “machined” out of silicon using the same processes commonly used to fabricate integrated circuits. These are often the same mechanical subassemblies that are part of their traditional macro-scale counterpart. Another attractive feature of MEMS is the ability to seamlessly integrate electrical and electro-mechanical components

Investigation of the applicability of current bridge health monitoring technology

Integrated health monitoring (HM) systems have been designed and installed in some long-span bridges around the world. One of the fundamental objectives of a bridge HM system is to gain a comprehensive knowledge of the structural condition, and usually it is required that early-stage damage in a bridge is detected within the monitored information. Yet the performance of the HM technology has not been evaluated in practice. The focus of this paper is to investigate the applicability of the current bridge HM technology for abnormality alarming. The deterioration and defects found from 16 cable-stayed bridges are summarized, and possible damage scenarios are simulated with a finite element model of a cable-stayed bridge. The changes in the static deformation and stress distribution as well as the dynamic characteristics of the bridge model due to damage are analysed. By comparison of the damage-caused changes in the structural behavior with the ability of the current monitoring techniques and the environmental effects, the workability of a typical bridge HM system is revealed. This may be helpful for the development of monitoring techniques and the design of HM systems.

振動・波動計測による場所打ちコンクリート杭の総合的ヘルスモニタリングに関する室内実験

An experimental study on the integrated health monitoring of cast-in-situ concrete pile foundations is presented using vibration and wave measurements. The health monitoring strategy is a two-stage damage detection scheme before and after excavation as in the case of the previous paper. A series of cyclic loading tests on cantilever-type specimens of cast-in-situ concrete pile have been performed to simulate the development of seismic damage. Four damage detection tests, i.e., vibration generator, impact hammer, acoustic emission and ultrasonic wave tests have been carried out during and after successive loading cycles. Based on the experimental results, the usefulness and limitations of the proposed damage detection scheme are discussed for cast-in-situ concrete pile foundations.

A Wrist-Worn Integrated Health Monitoring Instrument with a Tele-Reporting Device for Telemedicine and Telecare

In this paper, the prototype development of a wrist-worn integrated health monitoring device (WIHMD) with tele-reporting function for emergency telemedicine and home telecare for the elderly is reported. The WIHMD consists of six vital biosignal measuring modules, which include a fall detector, a single-channel electrocardiogram, noninvasive blood pressure, pulse oximetry (SpO2), respiration rate, and body surface temperature measuring units. The size of the WIHMD is 60times50times20 mm, except the wrist cuff, and the total system weighs 200 g, including two 1.5-V AAA-sized batteries. The functional objective of the WIHMD is to provide information concerning current condition, such as vital biosignals and locational information, with compromised fidelity to experts at a distance through the commercial cellular phone network. The developed system will provide the facility for rapid and appropriate directions to be given by experts in emergency situations and will enable the user or caregiver to manage changes in health condition with helpful treatment

Non-destructive characterization of smart CFRP structures

Smart materials based on carbon-fibre-reinforced plastic (CFRP) with embedded PZTsensors and actuators are expected to be a favourite composite for vibration damping andnoise reduction. Due to the wide variety of physical properties of the components, variousdamage mechanisms may reduce or even remove the sensing and actuating capabilities ofthe piezoceramic material. Comprehensive non-destructive characterization and integralhealth monitoring help to optimize the structure and its manufacturing and are essentialprerequisites to ensure performance and availability of smart components during theirlifetime. The first part of the paper presents high-resolution non-destructive imagingmethods including microfocus x-rays, ultrasonics and eddy currents. These methods areused to characterize damage resulting from non-optimal manufacturing and external load.The second part is dedicated to newly developed imaging techniques using the activepiezoceramics as transmitters of acoustic, electromagnetic and thermal fields. Thethird part focuses on health monitoring by impedance spectroscopy using thesame piezoceramics as for vibration damping. Electromechanical finite-elementmodelling and experimental investigations of strip-shaped specimens have shownthe close connection between mechanical properties and electrical impedance.

Transient modeling of Lamb waves emitted by integrated transducers using a hybrid finite element–normal mode expansion technique

For a few years, the concept of integrated health monitoring of aeronautic structures has become an important issue. A promising solution is the emission of ultrasonic Lamb waves using thin piezoelectric transducers integrated to the structure. Indeed Lamb waves are known to be able to propagate over long distance and to interact with inner structural defects. One important aspect when applying Lamb waves to health monitoring is the control and optimization of their generation. Therefore, a hybrid finite element–normal mode expansion modeling technique adapted to piezoelectric transducers has been recently developed. This technique allows the determination of the amplitude of each Lamb mode as a function of the transducer parameters. So far, it had been successfully applied to the case of harmonic excitation only. In this paper, adaptation of this hybrid technique to transient excitation is presented, which enables to simulate actual experimental conditions. Contrary to other techniques presented in the literature, the present technique allows to take into account the actual electromechanical behavior of the integrated transducer. Predicted results have been successfully compared to experimental measurements performed on different types of materials.

Adaptive Werkstoffsysteme und ihre zerstörungsfreie Charakterisierung

Adaptive Werkstoffsysteme auf der Grundlage carbonfaserverstärkter Laminate mit integrierten piezokeramischen Sensoren und Aktuatoren sind aussichtsreiche Komposite bei der Schwingungs- und Lärmdämpfung. Wegen der großen Bandbreite der physikalischen Eigenschaften ihrer Komponenten können spezifische Schädigungsmechanismen die sensorischen und aktuatorischen Wirkungen reduzieren. Die umfassende zerstörungsfreie Charakterisierung und das Health Monitoring leisten einen wesentlichen Beitrag bei der Entwicklung geeigneter Herstellungsverfahren und zur Strukturüberwachung. Adaptive material systems and their non-destructive characterisation Smart materials based on carbon fiber-reinforced plastics with embedded piezoceramic sensors and actuators are expected to be a favorite composite for vibration damping and noise reduction. Due to the wide variety of physical properties of the components various damage mechanisms may reduce the sensing and actuating capabilities of the piezoceramic material. Comprehensive non-destructive characterization and integral health monitoring help to optimize the structure and its manufacturing and are an essential prerequisite to ensure performance and availability of smart components during their life time.

Integrated Health Monitoring Approach for Reusable Cryogenic Tank Structures

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Comparison between Non-Destructive Evaluation Techniques and Integrated Fiber Optic Health Monitoring Systems for Composite Sandwich Structures

Non-Destructive Evaluation (NDE) methods have been adapted to composite sandwich structures in order to detect damage, in particular impact induced damage. Using three coupons representative of radome structures, several techniques were tested: ultrasonics, the Electromagnetic/InfraRed method (EMIR), stimulated shearography and stimulated infrared thermography. The extension of the measured damaged area was taken as a criterion, showing that stimulated shearography and ultrasound are the most sensitive methods. Moreover, two integrated Health Monitoring Systems (HMS) were tested, based on the one hand on microbending sensitive fibres and Optical Time Domain Reflectometry (OTDR), and on the other hand on Fibre Bragg Grating (FBG) sensors. The experiments demonstrated that HMS can detect damage with sensitivity comparable to that of the external NDE techniques.

An Integrated Health Monitoring Technique Using Structural Impedance Sensors

An Integrated Health Monitoring Technique Using Structural Impedance Sensors

An Integrated Health Monitoring Technique Using Structural Impedance Sensors

This paper presents an integrated methodology to detect and locate structural damage. Two different damage detection schemes are combined in this methodology, which involves utilizing the electromechanical coupling property of piezoelectric materials and tracking the changes in the frequency response function data, respectively. Physical changes in the structure cause changes in mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change in structural mechanical impedance causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance one can qualitatively determine when structural damage has occurred or is imminent. Based on the fact that damage produces local dynamic changes, this technique utilizes a high frequency structural excitation (typically greater than 30 kHz) through the surface-bonded piezoelectric sensor/actuators. As a second step, a newly developed model-based technique, using a wave propagation approach, has been used to quantitatively assess the state of structures. Direct frequency response function data, as opposed to modal data, are utilized to characterize the damage in the structures. A numerical example and an experimental investigation of one-dimensional structures are presented to illustrate the performance of this technique.

Condition monitoring of aircraft by quantitative filter debris analysis

AbstractVarious condition monitoring techniques are used collectively to monitor the health of aircraft engines and transmission, a concept known as Integrated Health Monitoring (IHM). A well‐established quantitative technique is Aircraft Oil Analysis (AOA), in which spectroscopic techniques such as Rotating Disk Electrode Atomic Emission Spectroscopy (RDE‐AES) are employed to analyse periodic oil samples for wear debris. Usually, no sample preparation is undertaken, as the oil sample containing both dissolved and suspended metallic wear debris is analysed directly. AOA works well for oil‐lubricated systems with relatively coarse filtration that allow circulation of the debris and its subsequent abrasive contact with moving components. To avoid this secondary wear, finer filtration is employed on both new and older aircraft. Less wear debris, and thus information, is available in the oil. A technique that quantitatively analyses the wear debris caught on the filter has been developed and is termed Quantitative Filter Debris Analysis (QFDA).Actual oil filters from CF88 Challenger ALF 502L‐2C and Hornet F404 engines were obtained in sequence, when possible, prepared by the developed procedure, and analysed with AOA instrumentation. With sufficient results, both normal and abnormal levels of wear rates emerged, as has been recorded and used for AOA. Moreover, trending of the data for sequential samples has demonstrated the capability of GFDA for condition monitoring.